Of the many ‘what ifs’ in history, the German invasion of Britain in 1940 is one that has been replayed many times. The reality was that the Germans were entirely unprepared for a cross-Channel invasion and lacked the means to transport a large force across the Channel and would have, had they tried, been blown out of the water by the Royal Navy. Nevertheless, impracticable though it was, the prospect of the enemy landing on Britain’s shores was regarded as a distinct possibility in the ‘invasion summer’ and every measure that could be taken was considered. The Auxiliary Units of the Home Guard were one of the most intriguing of those measures.

The principle of guerrilla action was a familiar one in warfare. Such movements, however, normally only developed after a country had been invaded. The proposal to create a guerrilla force to operate behind German lines in anticipation of an invasion was comparatively unique. There was, though, much evidence that small numbers of guerrillas could cause far more disruption amongst formed military units than their numbers would suggest and, in conjunction with regular forces, could prove highly effective. As early as 1939, shortly after the declaration of war, a British Military Intelligence (Research) notification stated: “If guerrilla warfare is co-ordinated and also related to main operations it should, in favourable circumstances, cause such a diversion of enemy strength as eventually to present decisive opportunities to the main forces.”

The task of setting up such a force was handed to Colonel Colin Gubbins. Whilst most people in the summer of 1940 saw the south and south-east coasts as those in danger of invasion, Gubbins considered the whole of the coast from southern Wales eastwards round to Scotland as being at risk and he deployed his ‘stay behind’ auxiliaries accordingly. By the end of August 1940 the Auxiliary Unit organisation stretched as far north as Brechin on Scotland’s east coast, south to Land’s End, and north of the Bristol Channel as far as Pembroke Dock. The Auxiliaries epitomised the mood of the day. This was the era of the formation of the Army Commandos and the Special Operations Executive, and recruits for the Auxiliaries were readily found. Drawn from the civilian community, they very quickly numbered approximately 4,000 men.

The ‘patrols’ as they were termed were generally formed of six-man teams. Their hides or Operational Bases, a name chosen because, unlike ‘hide-out’, it suggested an offensive rather than a defensive purpose, were situated in the most inaccessible locations, or those that enemy troops would be unlikely or unprepared to investigate too closely. Suitable locations included excavations within muddy river banks or deep within inaccessible bramble-strewn woods. These Operational Bases generally had a vertical entrance shaft with a rebated blast wall at the bottom. They included a small kitchen, an Elsan toilet cubicle and space for six bunks.

The Auxiliaries were trained in unarmed combat by W.E. Fairbairn, the man who helped devise the famous Fairbairn-Sykes commando knife, with which all the Auxiliaries were equipped. Auxiliaries also carried side arms but their rifles were often limited to silenced, high-velocity examples with telescopic sites which were to be used to pick off German sentries or guard dogs and, that dreaded possibility, collaborators. They were also issued with large quantities of grenades and with plastic high explosives.

One former Auxiliary recalled practicing attacking General Montgomery’s V Corps HQ at Steyning in Sussex, in July 1940: “We put time pencils into his lawn, which exploded during his morning meeting. He was furious. He had no sense of humour whatsoever and he didn’t enjoy that one bit.”

Part of the success of the Blitzkrieg was the Germans ability to progress steadily through enemy territory following their initial breakthrough. They had developed what was termed the ‘dissected march’ which enabled infantry to keep close behind the armoured divisions. The objective of the Auxiliary Units was to cause so much disruption behind the front line that large numbers of German infantry would be compelled to stop to deal with them. This would limit the penetration possible by the German armour, allowing the regular forces to consolidate their defensive strength or to mount counter-attacks.

The Operational Bases were only stocked with two weeks food. It was not expected that the Auxiliaries would last any longer than that. Yet if they could restrict the depth of the German advance just long enough for the regulars and the Home Guard to hold the enemy and fight back then their sacrifice would not have been in vain.

Churchill’s Secret Defence Army is a thoroughly enjoyable read and easy to digest. It includes colour photographs of a number of the secret Operational Bases which show just how difficult to find such places would have been.